A curious symmetric decomposition of the (des, exc)-Eulerian polynomials

One of the most central result in combinatorics says that the descent statistic and the excedance statistic are equidistribued over the symmetric group. As a continuation of the work of Shareshian-Wachs (Adv. Math., 225(6) (2010), 2921--2966), we provide a curious t-symmetric decomposition for the generating polynomial of the joint distribution of the descent and excedance statistics over the symmetric group.